Electronic device enclosures and heatsink structures with thermal management features

ABSTRACT

An electronic device may have a housing in which electronic components are mounted. The electronic components may be mounted to a substrate such as a printed circuit board. A heat sink structure may dissipate heat generated by the electronic components. The housing may have a housing wall that is separated from the heat sink structure by an air gap. The housing wall may have integral support structures. Each of the support structures may have an inwardly protruding portion that protrudes through a corresponding opening in the heat sink structure. The protruding portions may each have a longitudinal axis and a cylindrical cavity that lies along the longitudinal axis. Each of the support structures may have fins that extend radially outward from the longitudinal axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 13/221,796 filedAug. 30, 2011 entitled “Electronic Device Enclosures and HeatsinkStructures with Thermal Management Features”, which is incorporatedherein by reference in its entirety.

BACKGROUND

This relates to electronic devices, and more particularly, to thermalmanagement features for electronic devices.

Electronic devices contain electronic components that are mounted withinhousings. For example, an electronic device may contain integratedcircuits. During operation, electronic components such as integratedcircuits produce heat. If care is not taken, the heat from components inan electronic device may produce localized hot spots. The hot spots canmake some portions of the housing of the device undesirably warmrelative to other portions.

It would therefore be desirable to be able to provide improved housingconfigurations for electronic devices.

SUMMARY

An electronic device may have a housing in which electronic componentsare mounted. The electronic components may be mounted to a substratesuch as a printed circuit board. During operation, the electroniccomponents may generate heat.

A heat sink structure may be mounted adjacent to the electroniccomponents to dissipate the heat generated by the electronic components.The housing may have a housing wall that is separated from the heat sinkstructure by an air gap.

The housing wall may have support structures that separate heat sinkstructure from the housing wall to produce the air gap. Each of thesupport structures may have a protruding portion that passes through acorresponding opening in the heat sink structure. The protrudingportions may each have a longitudinal axis and a cylindrical cavity thatlies along the longitudinal axis. A tip portion of each protrudingportion may be bent using a heat staking process to attach the heat sinkstructure to the housing wall. Each of the support structures may haveshoulder portions formed from fins that extend radially outward from thelongitudinal axis.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device inaccordance with an embodiment of the present invention.

FIG. 2 is a cross-sectional side view of a device of the type shown inFIG. 1 showing how components may be mounted to a heat sink structure ina housing in accordance with an embodiment of the present invention.

FIG. 3 is a cross-sectional side view of a portion of a heat sinkstructure and housing in the vicinity of a support structure that isused to heat stake the heat sink structure to the housing in accordancewith an embodiment of the present invention.

FIG. 4 is a top view of a heat stake support structure of the type shownin FIG. 3 in accordance with an embodiment of the present invention.

FIG. 5 is a cross-sectional side view of an illustrative electronicdevice housing and heat sink with recessed areas and protruding areas tomanage the flow of heat from internal components in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

Thermal management features may be incorporated into an electronicdevice to control the flow of heat from internal device components. Anillustrative electronic device of the type that may be provided withthermal management features is shown in FIG. 1. Electronic device 10 ofFIG. 1 may be a computer, a set-top box, a wireless access point, aportable electronic device, or any other suitable electronic equipment.Configurations for electronic device 10 in which device 10 isimplemented as a wireless access point are sometimes described herein asan example. This is, however, merely illustrative. Electronic device 10may include any suitable type of electronic equipment if desired.

As shown in FIG. 1, electronic device 10 may have a housing such ashousing 12. Housing 12 may be formed from materials such as plastic,glass, ceramic, metal, carbon fiber, fiberglass, and other fibercomposites, other materials, or combinations of these materials. Housing12 may have one or more parts. For example, housing 12 may have matingupper and lower parts formed from plastic or other housing materials. Ifdesired, housing 12 may have more than two parts. In the configurationshown in FIG. 1, housing 12 has a rectangular box shape with planarupper and lower surfaces and four perpendicular (vertical) planarsidewalls. The corners of housing 12 may be rounded. Other shapes may beused for housing 12 if desired (e.g., shapes with curved sides, shapeswith circular footprints, shapes with combinations of curved andstraight edges and surfaces, etc.). The example of FIG. 1 is merelyillustrative.

To accommodate connectors for displays, device peripherals, powercables, and other accessories, housing 12 may have openings (e.g., portopenings) such as openings 14.

Device 10 may contain internal electronic components such as integratedcircuits and other components that generate heat. Thermal managementfeatures may be incorporated into the structures of device 10 to controlthe flow of heat from the interior to the exterior of housing 12.

A cross-sectional side view of an illustrative electronic device withthermal management features is shown in FIG. 2. As shown in FIG. 2,device 10 may have a housing 12 with planar upper housing wall 12A,planar lower housing wall 12B, and planar sidewalls such as leftsidewall 12C and right sidewall 12D. Electrical components 24 may bemounted within housing 12. Electrical components 24 may includeintegrated circuits, switches, sensors, input-output devices, wirelesscircuits, discrete components such as resistors, capacitors, andinductors, power supply components, displays, audio components, andother electronic equipment. During operation, electrical components 24may generate heat.

Electrical components 24 may be mounted on one or more substrates suchas substrate 26. Substrates such as substrate 26 may be rigid printedcircuit boards (e.g., printed circuit boards formed fromfiberglass-filled epoxy such as FR4 printed circuit boards), flexibleprinted circuits (“flex circuits”) formed from flexible sheets ofpolymer such as polyimide, printed circuit boards that contain bothflexible and rigid portions (sometimes referred to as “rigid flex”boards), plastic, glass, ceramic, or other suitable substrate materials.

Components 24 may be electrically and mechanically connected tosubstrate structures 26 using solder, welds, conductive adhesive,fasteners, and other electrical and mechanical attachment mechanisms. Inthe example of FIG. 2, there are three components 24 mounted on a singlesubstrate 26. In general, device 10 may contain any suitable number ofcomponents (e.g., one or more, five or more, ten or more, etc.) and anysuitable number of substrates 26 (e.g., one or more, two or more, threeor more, five or more, ten or more, etc.). When multiple substrates areused for mounting components 24, cables such as flex circuit cables andother interconnection structures may be used to route signals betweendifferent substrates 26. Components 24 may be mounted on one or bothsides of substrate structures 26. In the example of FIG. 2, components24 are mounted to the underside (inner side) of substrate 26. Components24 may be mounted on the top side (outer side) of substrate 26 ifdesired.

Heat dissipation from components 24 may be promoted using one or moreheat sinks As shown in FIG. 2, for example, one or more heat sinks suchas heat sink 18 may be placed in contact with components 24 to dissipateheat produced by components 24. One heat sink 18 is shown in FIG. 2,but, in general, device 10 may contain any suitable number of heat sinks18 (e.g., one or more, two or more, three or more, five or more, ten ormore, etc.). The arrangement of FIG. 2 in which a single heat sink isused to dissipate heat from multiple components 24 is merelyillustrative. If desired, each component 24 may be provided with anindividual heat sink or heat sinks may be provided that are each used indissipating heat from a respective subset of component 24 in device 10.

Heat sink structures 18 may be formed from one or more materials thatexhibit satisfactory thermal conductivity. As an example, heat sinkstructures 18 may be formed from one or more metals such as aluminum(e.g., aluminum alloys), copper, etc. To enhance thermal transferbetween components 24 and heat sink structures 18, high thermalconductivity materials may be placed between components 24 and heat sinkstructures 18 (e.g., conformal thermal pads, heat sink compound, etc.).

One or more air gaps may be formed between the outermost surfaces ofheat sink structures 18 and the inner surfaces of housing 12. The airgaps may serve to retard heat flow from the interior of device 10 to theexterior of device 10. This retardation of heat flow may help ensurethat heat is distributed laterally so that hot spots are reduced. Airgaps may be provided locally or may be provided globally (e.g., overmost or all of the available surface of heat sink structures 18). In theexample of FIG. 2, air gap 20 is formed globally between the lower(outermost) surface of heat sink structures 18 and the upper (innermost)surface of lower planar housing wall 12B. Other types of air gaps andair gaps of locally varying thickness may also be used. If desired, someor all of an air gap may also be filled with a material such as foam orlow density plastic that has a low thermal conductivity instead of air.The example of FIG. 2 is merely illustrative.

With a configuration of the type shown in FIG. 2, heat that is locallyproduced in the vicinity of each component 24 travels into heat sink 18.Because of the presence of air gap 20, the heat in heat sink 18 tends tobecome evenly distributed laterally (in dimensions X and Y). Gap 20 maybe sufficiently thin (e.g., 5 mm or less, 4 mm or less, 3 mm or less, 2mm or less, 1 mm or less, etc.) to ensure that there is sufficient heattransfer outwards (in dimension Z) through housing wall 12B. Thisprevents the temperatures of components 24 from becoming too high duringoperation. The increase in the lateral spreading of heat within heatsink 18 that is produced by air gap 20 may ensure that there are few orno perceptible hot spots on housing 12 when the exterior of housing 12is touched by a user. Air gaps 20 may be interposed between heat sinkstructures 18 and any suitable surfaces of housing 12 (e.g., betweenheat sink structures 18 and the upper surface of housing 12, betweenheat sink structures 18 and the lower surface of housing 12, betweenheat sink structures 18 and sidewall surfaces of housing 12, and/orbetween heat sink structures 18 and other suitable housing surfaces).The example of FIG. 2 in which there is one gap 20 adjacent to housingwall 12B is merely illustrative.

Air gaps such as air gap 20 may be created by supporting heat sinkstructures 18 with support structures such as support structures 16.Support structures 16 may be formed from part of heat sink structures18, from housing structures such as part of housing 12, from internalframe structures, from combinations of these structures, or from othersuitable structures. There may be any suitable number of supportstructures in device 10 (e.g., four so that each of four corners of arectangular heat sink may be supported, six, eight, three or more,etc.). Support structures 16 may form spacers that serve to create adesired amount of separation for air gap 20. Support structures 16 maybe formed from discrete structures that are attached to housing 12 ormay be formed from part of housing 12.

With one suitable arrangement, which is sometimes described herein as anexample, support structures 16 may be formed from integral protrudingportions of housing wall 12. FIG. 3 is a cross-sectional side view of anillustrative support structure 16. As shown in FIG. 3, heat sinkstructures 18 may have openings through which portions 30 of supportstructures 16 protrude. For example, if there are four supportstructures 16 in device 10, heat sink structures 18 may have fourcorresponding openings for receiving respective portions 30 of the foursupport structures 16.

Support structures 16 may have shoulder structures 28 that support heatsink structures 18 and establish the size of air gap 20. Portions 30 mayhave the shape of a hollow cylinder. Cylindrical cavity 32 may runparallel to at least some of the length of support structures 16 alonglongitudinal axis 33 of portions 30. Portions 30 of support structures16 may form a heat stake attachment structure that is deformed uponapplication of heat. In particular, the tips of portions 30 may beheated and bent downwards to positions 30′ during application of heat tothe tips of portions 30 in a heat staking process. In this position,heat stake portions 30 may be received within circular recess 34 of heatsink structures 18 to attach (heat stake) heat sink structures 18 tohousing 12B. The presence of an internal cavity within the protrudingcylindrical portion 30 of support structures 16 may help to reducethermal transfer between heat sink 18 and housing 12B. In the absence ofcavity 32, heat might be transferred from heat sink 18 to location 35 ofhousing 12B so effectively that location 35 of housing 12B might exhibitan unsightly heat-induced depression (sink mark).

Localized thermal transfer between heat sink structures 18 and housing12B can also be minimized by minimizing the footprint of shoulderportions 28 of support structures 16. With one suitable arrangement, thesurface area on housing 12B that is consumed by shoulder portions 28 maybe minimized by forming portions 28 in the shape of a set of fins thatprotrude radially outward from cavity 32 and longitudinal axis 33 ofcavity 32. FIG. 4 is a top view of support structures 16 that have beenformed using this type of approach. As shown in FIG. 4, portions 28 ofsupport structures 16 may include four radially extending fins 28A, 28B,28C, and 28D. Areas 35 between the fins are free of support structures16. Because air is present in areas 35, thermal transfer through areas35 and therefore through support structures 16 is minimized, reducingthe likelihood of forming a sink mark under support structures 16. TheFIG. 4 example includes four fins, but support structures 16 may haveone or more fins, two or more fins, three or more fins, four or morefins, etc.

FIG. 5 is a cross-sectional side view showing how the thickness of airgap 20 may be adjusted locally to help evenly distribute heat on theexterior surface of housing 12. As shown in FIG. 5, the thickness of gap20 may have different magnitudes in different locations. In some areas,the thickness of gap 20 may have a nominal thickness of T. In regions ofdevice 10 where it is desired to decrease thermal resistance, thethickness of gap 20 may be locally decreased to a value below nominalthickness T. When it is desired to increase thermal resistance, thethickness of gap 20 may be increased to be larger than nominal thicknessT. As an example, if it is desired to retard the flow of heat under acomponent that has an area of 1 cm², a 1 cm² area of device 10 thatoverlaps the component may be provided with an increased air gapthickness. If particular regions of device 10 are generating smallamounts of heat, the thickness of air gap 20 may be reduced in thoseregions.

In the example shown in FIG. 5, air gap thickness adjustments have beenmade using combinations of recessed areas and protruding areas in heatsink structures 18 and in housing wall 12B.

In area T−D1, the thickness of air gap 20 has been decreased to a valueof T−D1 by creating protrusion 36 in this area on the lower (outermost)surface of heat sink structures 16. Protrusion 36 has a thickness of D1,which reduces the thickness of air gap 20 by D1 over the area covered byprotrusion 36.

In area T+D2, the thickness of air gap 20 has been increased to a valueof T+D2 by creating recess 38 in this area on the upper (innermost)surface of housing wall 12B. Recess 38 has a depth of D2, whichincreases the thickness of air gap 20 by D2 throughout the area coveredby recess 38.

In area T−D3−D4, an air gap thickness adjustment has been made usingprotrusions on both heat sink structures 18 and housing wall 12B. Inparticular, the thickness of air gap 20 has been decreased to a value ofT−D3−D4 by creating protrusion 40 in this area on the lower (outermost)surface of heat sink structures 16 and by creating protrusion 42 on theupper (innermost) surface of housing wall 12B. Protrusion 40 has athickness of D4 and protrusion 42 has a thickness D3, so there is anoverall reduction in the thickness of air gap 20 from T to T−D3−D4 overthe area covered by protrusions 40 and 42. Protrusions 40 and 42 may,for example, have the same surface area and may have identicalfootprints (as an example).

In area T+D5, the thickness of air gap 20 has been increased to a valueof T+D5 by creating recess 44 in this area on the lower (outermost)surface of heat sink structure 18. Recess 38 has a depth of D2, whichreduces the thickness of air gap 20 by D2 throughout the area covered byrecess 44.

In area T−D6, the thickness of air gap 20 has been decreased to T−D6 bycreating a protrusion on housing wall 12B having a thickness of D6.

These are merely illustrative configurations for forming thermalmanagement features in device 10. In general, any suitable combinationsof protrusions and recesses on housing walls 12 and/or heat sinkstructures 18 may be used to narrow and/or expand air gap 20 and therebycontrol the flow of heat through air gap 20 and the evenness with whichheat spreads throughout dimensions X and Y before escaping outwardsthrough housing 12 (housing wall 12B) in dimension Z. If desired,additional layers of material, protrusions on other surfaces of heatsink structures 18, housing walls 12, and/or other structures in device10 may be used in controlling the flow of heat in device 10.Arrangements of the type shown in FIG. 5 are merely illustrative.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. An electronic device having an electricalcomponent, the electronic device comprising: a housing having a housingwall, the housing wall having at least one support structure protrudingfrom an internal surface of the housing wall, the housing wallcontinuous with the at least one support structure, the at least onesupport structure having a shoulder portion and a shaft portion thatextends from a top surface of the shoulder portion; and a heat sinkstructure positioned between the housing wall and the electricalcomponent and arranged to absorb heat generated by the electricalcomponent, the heat sink structure having at least one opening thataccepts the shaft portion of the at least one support structure, whereinthe shoulder portion separates the housing wall from the heat sinkstructure by a gap corresponding to a height of the shoulder portion,the gap decreasing an amount of heat transferred from the electricalcomponent to the housing wall.
 2. The electronic device of claim 1,wherein the shoulder portion is arranged to support the heat sinkstructure.
 3. The electronic device of claim 1, wherein the shaftportion aligns the heat sink structure with respect to the housing wall.4. The electronic device of claim 1, wherein the shoulder portion has alarger width than the shaft portion.
 5. The electronic device of claim1, wherein the heat sink structure includes an upper surface and a lowersurface, the at least one opening is disposed through both the uppersurface and the lower surface.
 6. The electronic device of claim 5,wherein a tip of the shaft portion extends above the upper surface ofthe heat sink structure.
 7. The electronic device of claim 6, whereinthe tip of the shaft portion is bent such that the tip secures the heatsink structure to the housing.
 8. The electronic device of claim 1,wherein the shaft portion has a hollow cavity.
 9. The electronic deviceof claim 1, wherein the shoulder portion includes a plurality of finsradially extending from the shaft portion.
 10. The electronic device ofclaim 1, wherein the housing wall includes a sidewall adjacent thehousing wall, wherein the at least one support structure is positioned asecond distance from the sidewall.
 11. A method of forming a heatdissipating assembly within a housing for an electronic device, themethod comprising: forming a housing having a housing wall, the housingwall having at least one support structure protruding from an internalsurface of the housing wall, the housing wall continuous with the atleast one support structure, the at least one support structure having ashoulder portion and a shaft portion that extends from a top surface ofthe shoulder portion; and positioning a heat sink structure positionedbetween the housing wall and an electrical component and such that theheat sink structure absorbs heat generated by the electrical component,the heat sink structure having at least one opening that accepts theshaft portion of the at least one support structure, wherein theshoulder portion separates the housing wall from the heat sink structureby a gap corresponding to a height of the shoulder portion, the gapdecreasing an amount of heat transferred from the electrical componentto the housing wall.
 12. The method of claim 11, wherein the heat sinkstructure includes an upper surface and a lower surface, the at leastone opening is disposed through both the upper surface and the lowersurface and wherein a tip of the shaft portion extends above the uppersurface of the heat sink structure, the method further comprising:bending a tip of the shaft portion such that the tip secures the heatsink structure to the housing.
 13. The method of claim 11, wherein thepositioning the heat sink structure comprises: aligning the shaftportion of the at least one support structure with corresponding atleast one opening.
 14. The method of claim 11, wherein the positioningthe heat sink structure comprises supporting the heat sink structure onshoulder portion of the at least one support structure.
 15. Anelectronic device having a heat generating component, the electronicdevice comprising: a housing having a housing wall, the housing wallhaving a plurality of support structures protruding from an internalsurface of the housing wall, each of the support structures having ashoulder and a shaft that extends from a top surface of the shoulder,each of the shoulders including a plurality of fins radially extendingfrom a corresponding shaft; and a heat sink structure positioned betweenthe housing wall and the heat generating component and arranged toabsorb heat generated by the heat generating component, the heat sinkstructure having a plurality of openings that accepts shafts ofcorresponding support structures such that the corresponding supportstructures cooperate to support the heat sink structure, wherein theshoulder separates the housing wall from the heat sink structure by agap corresponding to a height of the shoulder, the gap decreasing anamount of heat transferred from the heat generating component to thehousing wall.
 16. The electronic device of claim 15, wherein the shaftsof the plurality of support structures cooperate together to align theheat sink structure with respect to the housing wall.
 17. The electronicdevice of claim 15, wherein each of the shafts includes a hollow cavity.18. The electronic device of claim 15, wherein each of the plurality ofsupport structures is continuous with the housing wall.